In assembly lines for motor vehicle bodywork, subassemblies (such as the subframe, the sides of the body, the rear panel, . . . ) are put into position relative to one another and relative to welding robots. Since bodywork pieces are naturally deformable when subjected to stresses, the tooling used for making bodywork of determined and reproducible shape performs two functions: firstly it constitutes reinforcement for each of the deformable subassemblies so as to stiffen them, and secondly it constitutes a stable interface providing accurate positioning in a fixed frame of reference defined relative to the welding robots.
In a recently developed method of building motor vehicle bodies, the step of assembling the bodywork includes a stage of putting two body sides and a rear panel into place and holding them in position in the frame of reference of the assembly station by means of two parallel side tools each co-operating with one of the sides of the body and by means of a transverse tool co-operating with the rear panel, the three tools being connected to one another and to the frame of reference of the assembly station in such a manner that the transverse tool is placed and held in said frame of reference in a position that is precise and locked, and in such a manner that it forms a spacing and bracing tool for the two tools that are parallel in a direction perpendicular thereto.
Depending on the type of body to be assembled, it is necessary either for the rear panel to be put into place initially so that the sides of the body can then come up on either side thereof, or else for the sides of the body to be put into place initially so that the rear panel can then be fitted over the corresponding ends thereof. In addition, in order to increase productivity, it can be advantageous for the three tools to be capable of engaging or disengaging mutually relative to one another simultaneously so as to save time. Unfortunately, known means for holding two pieces in position relative to each other allow for only one direction in which said pieces can be engaged relative to each other such that incorporating such means in the above-described assembly station for interconnecting the tools would require the tools to be put into place successively at least to some extent and in a predetermined order. That limits the flexibility and the maximum productivity of the method.